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Genetics of phytate phosphorus bio-availability in poultry.

Abstract

Phosphorus is an essential mineral required in poultry diets for normal growth and development. It plays an important role in the metabolism of carbohydrates, amino acids and lipids. To meet metabolic demands, poultry of each species and age require specific amounts of phosphorus readily available for absorption and utilization. In broiler chickens, the amount of phosphorus required varies from 0.45 % per 100 g of diet to 0.3 %, depending on the age of the broiler (NRC, 1994). About 70 % of all phosphorus in plant products is present as phytate (phytic acid) or its salts, and is essentially unavailable to poultry because chickens lack adequate levels of the enzyme phytase, which is needed to hydrolyze phytate and release phosphorus for absorption and utilization. The inability to utilize phytate phosphorus results in a substantial loss of nutrient efficiency and creates a significant pollution threat when manure containing residual phosphorus is applied to land. Punna and Roland (1996) demonstrated that variation in phytate phosphorus utilization in the same strain of chicken is related to growth, livability and skeletal strength. Carlos and Edwards (1997) further observed large individual differences in phytate phosphorus utilization with a strain when fed phosphorus deficient diets with or without phytase. Thus, it appears that there is genetic variation between birds of different breeds and within the same strain as well. The large variability within a strain (Edwards, 1983 ; Punna and Roland, 1996 ; Carlos and Edwards, 1997) suggests that chickens can be selected for phytate phosphorus utilization with success. Genetic modification of birds for phytate phosphorus utilization provides us with a permanent, long-term solution to environmental pollution problems. In this paper we report the inheritance of phytate phosphorus utilization and the relationship between phytate phosphorus utilization and progeny body weight.